Precipitation dynamics in Ecuador and northern Peru during the 1991/92 El Nino: A remote sensing perspective

Resumen

Abstract. The formation, dynamics and spatial distribution of heavy precipita-tion during the 1991/92 El Niño in Ecuador and northern Peru were examined by means of Meteosat-3 imagery, NOAA-AVHRR-based multichannel sea surface temperatures (MCSST) and additional meteorological observations. The Convective and Stratiform Technique (CST) was used for rain retrieval by means of Meteosat IR data and a cross-correlation approach was applied to Meteosat image sequences to derive cloud motion winds (CMW) which are essential for the analysis of circulation patterns leading to severe precipitation. From an analysis of 45 days with severe precipitation it is proven that three mechanisms were responsible for the formation of heavy rains. Each mechanism reveals a speci c localized impact. (1) The most frequent mechanism (frequency of ~61%) represents an extended land–sea breeze system. During such weather conditions, predominantly locally con ned precipitation patterns occured. Areas a ected by the sea wind front during the day were the coastal plains up to the 1000m contour line on the western Andean slope. Local maxima in the frequency of cloudiness